The 40-year-old singer confirmed the exciting news on Twitter Monday, writing, "Ayda [Field] and I are are delighted to announce that Theodora Rose Williams is going to be a big sister."

Little Theodore, who goes by Teddy, turns 2 this September, and according to her famous father, she's given him a new lease on life. "Everything I do is for her," the former Take That member said in a 2013 interview with BBC Radio 4.

"There's a reason for me to do everything now," he elaborated. "I wasn't going to have a kid and I wasn't going to get married then I met someone who was amazing and fell in love with her completely and I changed all my thoughts and feelings about that." (Robbie said goodbye to his bachelor days in August 2010, when he and Anya, 34, tied the knot at their Beverly Hills, Calif., home.)

"It's a miracle that it has happened because I now get to experience the full gamut of being human," he continued. "She's a sensational kid."

Robbie, who admitted he was "very selfish for a long time" and "didn't have to lift a finger" for most of his adult life, told BBC Radio 4 he was "terrified all through the pregnancy [with Teddy] that I wasn't going to be able to step up and be a father, the father that I want to be to her."

But the singer "made a promise to her during that time" that he'd do his best, saying he realized raising his child would be "the most important job I will do on the planet."